This new research, as yet unpublished, raises crucial and emotive questions about how far the boundaries of science and technology should continue to be pushed and how far should doctors go to resuscitate babies born at the limits of viability.

The study followed up all premature babies born alive at less than 26 weeks gestation in Britain during 1995.

The researchers - who include some of Britain's leading neonatologists - have given Panorama unique access.

The findings reveal how the children had developed by the age of six, how many have physical or learning disabilities and how many grew up without disability.

Panorama has also been given exclusive access to children and their families who took part in the study who share their stories in the programme.

Some parents are grateful to have a child whatever the outcome. However others have said, there have been times when they wondered whether it might have been better to allow their babies to die.